The designer peptides RADA16-I and MAX8 self-assemble into nanofiber matrices capable of supporting cell culture and regenerative medicine. The peptides were designed with repetitive amino acid sequences which promote �-strand secondary structure and self-assembly via backbone hydrogen bonding. In the literature, RADA16-I is presumed to form an antiparallel �-sheet structure, minimizing repulsion between like-charged sidechains. MAX8 includes a type II' double proline turn, which is proposed to affect triggered self-assembly via ion-dependent �-hairpin formation. We have tested both structural hypotheses by solid state NMR spectroscopy. NMR data on 13C chemical shift and 13C-13C dipolar coupling within RADA16-I nanofibers are not consistent with antiparallel �-sheet structure, but support a structure composed of parallel �-strands. Data on 13C-13C dipolar couplings within MAX8 nanofibers are consistent with the proposed �-hairpin conformation. Both peptides have some polymorphic tendency. These results will be discussed in the context of our predictive ability in the design of peptides which self-assemble through �-sheet formation.RADA16-I nanofiberMAX8 �-hairpin

Molecular structures of RADA16-I and MAX8 self-assembled �-sheet peptide nanofibers probed by solid state NMR spectroscopy

247th National Meeting (2014)

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